“…without rapid and massive action, the problem will be about twice as severe as previously estimated six years ago – and could be even worse than that…. The study uses the MIT Integrated Global Systems Model, a detailed computer simulation of global economic activity and climate processes that has been developed and refined by the Joint Program on the Science and Policy of Global Change since the early 1990s. The new research involved 400 runs of the model with each run using slight variations in input parameters, selected so that each run has about an equal probability of being correct based on present observations and knowledge.”

The study reports, among other items, that there is a median probability of 5.2 degrees Celsius warming by 2100, compared to a projected 2.4 degree warming in a 2003 study.